Protagonists in the novels of Saul Bellow, like Albert Corde in “The Dean’s December,” are known for struggling with the “big-scale insanities of the 20th century.” The same might be said about the main character in Viet Thanh Nguyen’s canny, audacious debut novel, “The Sympathizer” (Grove Press, 371 pp., $26).

The epic insanity in this story is the Vietnam War. Nguyen, who was born in Vietnam and raised in the U.S., tells the tale from a unique and startling perspective: an unnamed Vietnamese narrator who is a double agent for the fallen South Vietnamese regime and the Viet Cong victors.

“I am a spy, a sleeper, a spook, a man of two faces,” begins the narrator’s 295-page “confession” delivered to the Commandant, a postwar communist leader in Vietnam. But far from a conventional or (from the Commandant’s perspective) satisfactory confession, this one wanders far afield, providing the author with a broad canvas to recount his character’s personal history amid real historical events.

Because of his smarts and near-native command of English — he spent six years at an American university in the 1960s — the narrator was recruited by the CIA and eventually becomes the right-hand man to a South Vietnamese army general, both in Vietnam and after his escape from his homeland. But the narrator was already a loyal communist and clandestinely continues this role after he resettles in Los Angeles, filing regular reports to his Parisian “aunt” using code written in invisible ink.

The narrator is “double” in another significant sense that frames this work: He’s biracial, with a Vietnamese mother and a French father, a mixed-race “bastard” who is bullied and ostracized his whole life.

Between plot peaks, Nguyen roams wildly, the better to explore many fascinating tangents. Nguyen’s prose is often like a feverish, frenzied dream, a profuse and lively stream of images sparking off the page. “Noses to the wind, we inhaled a farrago of scents: charcoal and jasmine, rotting fruit and eucalyptus, gasoline and ammonia, a swirling belch from the city’s poorly irrigated gut,” he writes about Saigon in the chaotic days before the Americans leave the city in April 1975.

As the story unfolds, the narrator is increasingly hard to figure. He has a few friends in L.A. and an American girlfriend, but he seems perpetually unmoored. Even though he is writing a confession, he often straddles the two opposing sides, sympathizing with “the enemy,” so that he operates from a murky morality. He is a communist but not a particularly ideological or zealous one.

Nguyen can be wickedly funny. After recounting how once proud, powerful military men are now doing menial work in the U.S., Nguyen writes: “So the list went, a fair percentage collecting both welfare and dust, moldering in the stale air of subsidized apartments as their testes shriveled day by day, consumed by the metastasizing cancer called assimilation and susceptible to the hypochondria of exile.”

Nguyen’s narrator has an incisive take on Asian-American history and what it means to be a nonwhite American. He displays a bracing sense of outrage at the depiction of Asians in Hollywood films, especially when he is hired as a consultant for an “Apocalypse Now” kind of war movie, filmed in the Philippines.

The story takes a dark turn in the last few chapters when the narrator returns to his homeland, part of the general’s ill-fated mission to foment counterrevolution, threatening to douse the novel’s sparkling energy. Imprisoned in solitary confinement for a year as he edits and refines his confession, the narrator undergoes horrific torture and “re-education.” But owing to some gymnastic plot twists and the foundation the author has already built, the narrative turns around, and the darkness serves as contrast to the coming light.

As we mark the 40th anniversary of the end of the Vietnam War, this remarkable, rollicking read by a Vietnamese immigrant heralds an exciting new voice in American literature.

David Takami is a writer who lives in Kenmore.